וְהָיָה מִתְעַנֶּה הַרְבֵּה מְאֹד, וְכַמָּה פְּעָמִים הִתְעַנָּה מִשַּׁבָּת לְשַׁבָּת, וְהַכֹּל בִּימֵי נְעוּרָיו מַמָּשׁ קֹדֶם הֱיוֹתוֹ בֶּן עֶשְׂרִים שָׁנָה. וְלִפְעָמִים הִתְעַנָּה שְׁנֵי פְּעָמִים מִשַּׁבָּת לְשַׁבָּת רְצוּפִים זֶה לָזֶה. The Rebbe engaged in many fasts. Even while still in his teens, he fasted from Shabbat to Shabbat many times (see “His Wisdom” #160-161). There were occasions when he fasted from Shabbat to Shabbat twice in succession.
וְאַף עַל פִּי שֶׁהָיָה "יֶלֶד שַׁעֲשׁוּעִים" וּמְגֻדָּל בְּתַפְנוּק, וְהָיָה אָדָם דַּק מְאֹד, אַף־עַל־פִּי־כֵן לֹא הָיָה חָס עַל־עַצְמוֹ כְּלָל, וְהִתְעַנָּה וְסִגֵּף עַצְמוֹ מְאֹד, וְהִתְעַנָּה חַ"י [שְׁמוֹנֶה־עֶשְׂרֵה] פְּעָמִים מִשַּׁבָּת לְשַׁבָּת בְּשָׁנָה אַחַת. Although the Rebbe was a child of delights (Jeremiah 31:19), raised in comfort, he was very thin. Still, he would disregard himself completely, fasting and mortifying himself in every possible way. Once he fasted from Shabbat to Shabbat eighteen times in a single year.